Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754370Ab1CHLWJ (ORCPT ); Tue, 8 Mar 2011 06:22:09 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35655 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753414Ab1CHLWH (ORCPT ); Tue, 8 Mar 2011 06:22:07 -0500 Message-ID: <4D761138.4030705@redhat.com> Date: Tue, 08 Mar 2011 12:21:28 +0100 From: Petr Holasek User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.14) Gecko/20110302 Fedora/3.1.8-0.38.b3pre.fc14 Thunderbird/3.1.8 MIME-Version: 1.0 To: Andrew Morton CC: Naoya Horiguchi , Dave Hansen , linux-kernel@vger.kernel.org, emunson@mgebm.net, anton@redhat.com, Andi Kleen , Mel Gorman , Wu Fengguang , linux-mm@kvack.org, Nishanth Aravamudan Subject: Re: [PATCH] hugetlb: /proc/meminfo shows data for all sizes of hugepages References: <1299503155-6210-1-git-send-email-pholasek@redhat.com> <1299527214.8493.13263.camel@nimitz> <20110307145149.97e6676e.akpm@linux-foundation.org> <20110307231448.GA2946@spritzera.linux.bs1.fc.nec.co.jp> <20110307152516.fee931bb.akpm@linux-foundation.org> In-Reply-To: <20110307152516.fee931bb.akpm@linux-foundation.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4340 Lines: 112 On 03/08/2011 12:25 AM, Andrew Morton wrote: > On Tue, 8 Mar 2011 08:14:49 +0900 > Naoya Horiguchi wrote: > >> On Mon, Mar 07, 2011 at 02:51:49PM -0800, Andrew Morton wrote: >>> On Mon, 07 Mar 2011 11:46:54 -0800 >>> Dave Hansen wrote: >>> >>>> On Mon, 2011-03-07 at 14:05 +0100, Petr Holasek wrote: >>>>> + for_each_hstate(h) >>>>> + seq_printf(m, >>>>> + "HugePages_Total: %5lu\n" >>>>> + "HugePages_Free: %5lu\n" >>>>> + "HugePages_Rsvd: %5lu\n" >>>>> + "HugePages_Surp: %5lu\n" >>>>> + "Hugepagesize: %8lu kB\n", >>>>> + h->nr_huge_pages, >>>>> + h->free_huge_pages, >>>>> + h->resv_huge_pages, >>>>> + h->surplus_huge_pages, >>>>> + 1UL<< (huge_page_order(h) + PAGE_SHIFT - 10)); >>>>> } >>>> >>>> It sounds like now we'll get a meminfo that looks like: >>>> >>>> ... >>>> AnonHugePages: 491520 kB >>>> HugePages_Total: 5 >>>> HugePages_Free: 2 >>>> HugePages_Rsvd: 3 >>>> HugePages_Surp: 1 >>>> Hugepagesize: 2048 kB >>>> HugePages_Total: 2 >>>> HugePages_Free: 1 >>>> HugePages_Rsvd: 1 >>>> HugePages_Surp: 1 >>>> Hugepagesize: 1048576 kB >>>> DirectMap4k: 12160 kB >>>> DirectMap2M: 2082816 kB >>>> DirectMap1G: 2097152 kB >>>> >>>> At best, that's a bit confusing. There aren't any other entries in >>>> meminfo that occur more than once. Plus, this information is available >>>> in the sysfs interface. Why isn't that sufficient? >>>> >>>> Could we do something where we keep the default hpage_size looking like >>>> it does now, but append the size explicitly for the new entries? >>>> >>>> HugePages_Total(1G): 2 >>>> HugePages_Free(1G): 1 >>>> HugePages_Rsvd(1G): 1 >>>> HugePages_Surp(1G): 1 >>>> >>> >>> Let's not change the existing interface, please. >>> >>> Adding new fields: OK. >>> Changing the way in whcih existing fields are calculated: OKish. >>> Renaming existing fields: not OK. >> >> How about lining up multiple values in each field like this? >> >> HugePages_Total: 5 2 >> HugePages_Free: 2 1 >> HugePages_Rsvd: 3 1 >> HugePages_Surp: 1 1 >> Hugepagesize: 2048 1048576 kB >> ... >> >> This doesn't change the field names and the impact for user space >> is still small? > > It might break some existing parsers, dunno. > > It was a mistake to assume that all hugepages will have the same size > for all time, and we just have to live with that mistake. > > I'd suggest that we leave meminfo alone, just ensuring that its output > makes some sense. Instead create a new interface which presents all > the required info in a sensible fashion and migrate usersapce reporting > tools over to that interface. Just let the meminfo field die a slow > death. The main idea behind this patch is to unify hugetlb interfaces in /proc/meminfo and sysfs. When somebody wants to find out all important informations about hugepage pools (as hugeadm from libhugetlbfs does), he has to determine default hugepage size from /proc/meminfo and then go into /sys/kernel/mm/hugepages/hugepages-kB/ for informations about next nodes. I agree with idea of throwing away of meminfo hugepage fields in the future, but before doing this, sysfs part of interface should indicate default hugepage size. And meminfo could possibly show data for all hugepage sizes on system. So when these parts will be independent, it is no problem to let meminfo fields die. > > It's tempting to remove the meminfo hugepage fields altogether - most > parsers _should_ be able to cope with a CONFIG_HUGETLB=n kernel. But > that's breakage as well - some applications may be using meminfo to > detect whether the kernel supports huge pages! -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/